Anomalous number of ribs

An anomalous number of ribs is defined as variant anatomy. Most commonly people have 12 rib bearing thoracic vertebrae. Some people are born with either fewer or more than 12 ribs attached to the vertebral bones of the spine.Extra ribs, also called accessory ribs, can occur above the rib cage and at this location are called cervical ribs because they attach to the cervical spine of the neck. Accessory ribs can also occur at the bottom of the rib cage giving 13 or more rib bearing thoracic type vertebra.Occasionally incomplete tiny ribs can occur, most commonly at the bottom of the rib cage, and these are called 'rudimentary' or 'vestigeal' ribs and they are assigned to the lumbar type vertebrae of the lower back.Fewer than 12 thoracic vertebrae can also occur, with the 'missing' rib(s) being at the lower part of the ribcage. This can result in the most common rib count variant of 11 thoracic type vertebrae. The number of thoracic (rib bearing) vertebrae is important to know, because in medicine landmarks for the lumbar spine levels are often (erroneously) counted based on the number of ribs seen, with the first lumbar vertebra assigned as the one without a bony rib even if it has a rudimentary rib. This erroneous counting usually occurs because only a part of the spine is imaged.Knowing the presence of this variant anatomy is essential if any surgery is planned, as X-rays easily see the ribs and thus the counting of the ribs and vertebrae is used for surgical planning.Pateints with an anomalous number of ribs usually remain entirely asymptomatic, however in some people accesory (extra) ribs can become problematic by causing pain, lack of mobility, soft tissue irritation, or nerve compression anytime now or in the future. Understanding your medical history and preventing irritation to these potentially susceptible areas is important to know if and when symptoms occur.